Field of the Invention
The disclosed and claimed concept relates to a vacuum circuit breaker and, more specifically, to a vacuum circuit breaker including a conductive member with an electro-thermally efficient contour.
Background Information
Circuit breakers and other such devices provide protection for electrical systems from electrical fault conditions such as current overloads, short circuits, and low level voltage conditions. In one embodiment, circuit breakers include a spring-powered operating mechanism which opens electrical contacts to interrupt the current through the conductors in an electrical system in response to abnormal conditions. In particular, vacuum circuit interrupters include separable main contacts disposed within an insulated and hermetically sealed vacuum chamber within a housing.
The contacts are part of an electrode including a stem and a contact member. Generally, one of the electrodes is fixed relative to the housing. The other electrode is moveable relative to the housing and the other electrode. An operating mechanism is structured to move the movable contact between a first configuration, wherein the movable contact is spaced from, and is not in electrical communication with, the fixed contact and a second configuration, wherein the movable contact is directly coupled to, and is in electrical communication with, the fixed contact. In this configuration, a vacuum interrupter is structured to interrupt medium voltage alternating current (AC) and, also, high voltage AC currents of several thousands of amperes or more. In one embodiment, one vacuum interrupter is provided for each phase of a multi-phase circuit and the vacuum interrupters for the several phases are actuated simultaneously by a common operating mechanism, or separately or independently by separate operating mechanisms. The electrodes can commonly take three positions: closed, opened and grounded.
The electrodes are also part of a larger conductor assembly that includes a first terminal, a primary first conductor, a primary second conductor and a second terminal. The first terminal is structured to be coupled to, and in electrical communication with, either a line or a load. The first terminal is coupled to, and in electrical communication with, the primary first conductor. The primary first conductor is coupled to, and in electrical communication with, the fixed electrode. The second terminal is structured to be coupled to, and in electrical communication with, the other of either a line or a load. The second terminal is coupled to, and in electrical communication with, the primary second conductor. The primary second conductor is coupled to, and in electrical communication with, the movable electrode.
The first and second primary conductors are generally made from either generally cylindrical copper members or a number of generally planar copper members. In some instances planar copper members are bent. Further, in some instances, multiple planar copper members are disposed in a stack. Such conductors have several disadvantages.
For example, such conductors are subjected to a “skin effect.” As used herein, a “skin effect” is the tendency of an alternating electric current to become distributed within a conductor such that the current density is largest near the surface of the conductor, and decreases with greater depths in the conductor. That is, the “skin effect” tends to push the current towards the outer surface of a conductor, therefore the inner portions of the conductor have a lower current density than the outer portions. Stated alternately, such primary conductors do not have an electrically efficient contour. Further, such primary conductors generate heat as current passes therethrough. The disclosed contours are not adapted to dissipate heat. Stated alternately, such primary conductors do not have a thermally efficient contour.
Further, with regard to primary conductors made from planar members, the planar members tend to have sharp edges. Such sharp edges contribute to the formation of arcs between elements. Also, primary conductors made from copper contribute to all the problems stated above.
There is, therefore, a need for a conductive member that is not subject to the disadvantages identified above. Further, there is a need for a conductive member that is usable in existing circuit breakers.